1. Field of the Invention
The present general inventive concept relates to a piezoelectric inkjet head, and more particularly, to a piezoelectric inkjet head including restrictors and nozzles that are symmetrically arranged with respect to a pressure chamber.
2. Description of the Related Art
An inkjet head is a device for printing a predetermined color image by ejecting minute droplets of ink on desired areas of a printing medium. Inkjet heads can be generally classified into various types according to their method of ejecting ink droplets. One type is a thermal inkjet head that ejects ink droplets using the expansion force of ink bubbles created using a heat source, and the other type is a piezoelectric inkjet head that ejects inkjet droplets using a pressure created by the deformation of a piezoelectric element.
Piezoelectric inkjet heads have been used in an industrial inkjet printer as well as an inkjet printer for office automation (OA), and have also been variously used in printing fields in which high precision is required when manufacturing a color filter for a liquid crystal display device (LCD), an organic light emitting diode (OLED) or metal jetting.
FIG. 1 is a plan view of a conventional piezoelectric inkjet head. FIG. 2 is a cross-sectional view of the conventional piezoelectric inkjet head taken along a line A-A′ of FIG. 1.
Referring to FIGS. 1 and 2, the conventional piezoelectric inkjet head includes a flow channel plate 20 in which an ink flow channel is formed, a nozzle plate 30, in which a plurality of nozzles 32 from which ink is ejected, is formed, and a plurality of piezoelectric actuators 40. Both of the flow channel plate 20 and the nozzle plate 30 are formed of silicon. A manifold 21, a plurality of restrictors 23 and a plurality of pressure chambers 22 are formed in the flow channel plate 20. The manifold 21 is a channel through which ink inflows from an ink storage (not shown). The pressure chambers 22 are places filled with ink that is to be ejected, and are arranged in one side or both sides of the manifold 21. The restrictors 23 are channels connecting the manifold 21 to the pressure chambers 22. Meanwhile, a plurality of dampers 24 and 31 connecting each of the nozzles 32 to each of the pressure chambers 22 is further formed between each of the nozzles 32 and each of the pressure chambers 22. In addition, the piezoelectric actuators 40 are disposed on the flow channel plate 20 to respectively correspond to the pressure chambers 22. The pressure chambers 22 have a stack structure of a lower electrode functioning as a common electrode, a piezoelectric film that changes according to a driving signal, and an upper electrode functioning as a driving electrode. The flow channel plate 20, disposed with the pressure chambers 22, functions as a vibration plate 26 that is transformed by driving the pressure chambers 22.
In the conventional piezoelectric inkjet head having such structure, when a driving signal is supplied to the pressure chambers 22, the vibration plate 26, which is disposed above each the pressure chambers 22, is transformed. In this case, the volumes of the pressure chambers 22 are reduced, and thus ink is ejected outside through the nozzles 32 due to the increase in the pressure inside the pressure chambers 22. Then, when the driving signal that is supplied to the pressure chambers 22 is removed, the volumes of the pressure chambers 22 increase, and thus ink is refilled into the pressure chambers 22 from the manifold 21 through the restrictors 23 due to the reduction in the pressure inside the pressure chambers 22.
However, in the conventional piezoelectric inkjet head, each of the restrictors 23 is connected to one end of each of the pressure chambers 22, and each of the nozzles 32 is connected to the other end of each of the pressure chambers 22. Thus, since the propagation path of a pressure wave P that is generated by driving the piezoelectric actuators 40 is increased as illustrated in FIG. 2, loss in the intensity of the pressure wave P, which is propagated to the nozzles 32, is incurred. A direction of the pressure wave P does not correspond to a longitudinal direction of each of the nozzles 32. Accordingly, the meniscus of the ink of the nozzles 32 is unstable, and the linearity of ink ejected from the nozzles 32 deteriorates. In addition, when a color filter is manufactured using a conventional piezoelectric inkjet head, ink droplets having a large volume are ejected to a local area of each pixel of the color filter, and thus ink may overflow outside a pixel.